

:;•( 



!ii:i 



^:-!> 



UNITED STATES DEPARTMENT OF AGRICULTURE 
BULLETIN No. 640 



Contribution from the Bureau of Entomology 
L. O. HOWARD. Chief 



Washington, D. C. 



April 8, 1918 



THE MEDITERRANEAN FRUIT FLY 



By 

E. A. BACK, Entomologist, and C. E. PEMBERTON, Assistant 

Entomologist, Mediterranean and Other 

Fruit Fly Investigations 



CONTENTS 



Page 
Distribution Thronehout the Worid . . 2 
Establishment and Spread in Hawaii . . 3 
How the Fruit Fly got into Hawaii « . . 4 
Losses Incurred Through the Fruit Fly . 5 
What the Mediterranean Fruit Fly is Like 7 
Fruits. Nuts, and Vegetables Attacked . 11 
Host Fruits of Commercial Value ... 15 
Artificial Methods of Control not Satis- 
factory Under Hawaiian Conditions . 24 



The Campaign Against the Fruit Fly in 

Hawaii ....«•• 26 

Natural Control of the Fruit Fly . ... 37 

Quarantine Measures to Prevent Intro- 
duction %.• 41 

Summary o 42 




WASHINGTON 
GOVERNMENT PRINTING OFFICE 

1918 






ONE OF THE WORST enemies of fruit grown in 
tropical and semitropical countries is the Medi- 
terranean fruit fly. Constant vigilance is necessary 
to prevent its establishment in North America. It is 
particularly destructive because it is difficult to con- 
trol and attacks many kinds of fruits, nuts, and vege- 
tables. In the Hawaiian Islands, where it has caused 
great damage since 1910, it attacks 72 kinds of fruits. 
A partial list of these contains oranges, grapefruit, 
lemons, limes, kumquats, tangerines, peaches, apples, 
figs, apricots, bananas, mangoes, avocados, sapotas, 
loquats, persimmons, guavas, quinces, papayas, 
pears, plums, grapes, eggplant, tomatoes, and even 
cotton bolls. Most of these are now grown or can be 
grown in our Southern States, the Gulf region, and 
California and the Southwest. 

The purpose of this bulletin is to give alike to the 
citizen of Hawaii, the fruit grower of the United 
States mainland, and the traveler information that 
will help to convey a clear conception of the difficult 
problem that has developed with the introduction of 
the Mediterranean fruit fly into the Hawaiian Is- 
lands. The pest can be kept out of the rich semi- 
tropical fruit-growing sections of the United States 
only by the hearty and intelligent cooperation of all. 



D. of D. 

APl^ 17 13*3 



UNITED STATES DEPARTMENT OF AGRICULTURE 




BULLETIN No. 640 



Contribution from the Bureau of Entomology 
L. O. HOWARD. Chief 




Washington, D. C. 



April 8, 1918 



THE MEDITERRANEAN FRUIT FLY. 



CONTENTS, 



Page. 

Distribution throughout the world 2 

Establishment and spread in Hawaii 3 

How the fniit fly got into Hawaii 4 

Losses incurred through the fruit fly 5 

What the Mediterranean fniit fly is lilcc 7 

Fruits, nuts, and vegetables attacked 11 

Host fruits of commercial value 15 



Page. 
Artificial methods of control not satisfactory 

under Hawaiian conditions 24 

The campaign against the fniit fly in Hawaii . . 21) 

Natural control of the fruit fly '.',7 

Quarentine measures to prevent introduction. 41 

Summary 42 



THE HORTICULTURAL DEVELOPMENT of the Haw^aiian 
Islands has been almost stopped since 1910 by the activity of two 
fruit-fly pests — the Mediterranean fruit fly^ and the melon fly.'^ 

These two pests are being intercepted continually by quarantine 
officials at our ports of entry and they are therefore feared by, and are 
of vital interest to, every fruit and vegetable grower in the warmer por- 
tions of the Pacific and Gulf coast States. Every possible barrier to 
the establishment of these pests on the mainland United States is being 
erected by the Federal Horticultural Board, working in cooperation 
with State officials. Quarantines now^ regidate the movement of 
horticultural products from infested countries; hence the greatest 
danger to California, Florida, and Mexican territory now lies in the 
unintentional spread of fruit-fly pests by uninformed travelers who 
may carry infested fruits upon their persons or in their baggage. 

The Mediterranean fruit fly (fig. 1) is one of the recently introduced 
pests of Hawaii. It has found climatic and food conditions so favor- 
able that at present there is not a family unaffected by its ravages. 
It is doubtful if there exist in any other place in the world conditions 
so favorable to the rapid spread and thorough establishment of this 
pest as those in the Hawaiian Islands. 

1 "The Mediterranean Fruit Fly in Hawaii," E. A. Back and C. E. Pemberton, Department of Agri- 
culture Bulletin 536. ( Ceratitis capitata Wied.) 

2 "The Melon Fly in Hawaii," E. A. Back and C. E. Pemberton, Department of Agriculture Bulletin 
491. {Bactrocera cucurbitae Coq.) 

3 "The Melon Fly," E. A. Back, C. E. Pemberton, Department of Agriculture Bulletin (U.'i. 

Note. — The manuscript of this paper was prepared for publication as a Farmers' Bulletin, but owing 
to the fact that it deals with an insect which has not yet been introduced into the United Stales it was 
considered more appropriate to issue it in the series of Department Bulletins. 
103876"— IS— Bull. 640 1 



2 BULLETIN ()40^ U. S. DEPARTMENT OF AGRICULTURE. 

DISTRIBUTION THROUGHOUT THE WORLD. 

The Mediterranean fruit fly is a cosmopolitan pest. It has been 
known to science for 100 years and during these years has spread 
tliroughout the world, until to-day the North American continent 
is the only large land area upon which it has not become established. 
It first attracted serious attention in London, where oranges^ arriving 
from the Azores were discovered to be badly decayed and wormy. 
(See fig. 2.) It was recorded as a pest in Spain in 1842, in Algeria 
in 1858, in Italy in 1868, in Sicily in 1878, and in Tunis in 1885. In 
1889 it was first reported in South Africa. It became established 
in the western part of Australia in 1897 and in the eastern part in 




Fig. 1.— Adult male Mediterranean fruit fly. Greatly enlarged . (Howard.) 

1898. In 1899 it was detected in Tasmania, in 1900 it was found 
attacking the apricot orchards near Paris, France, and during 1901 
it was reported from New Zealand and Brazil. Compere, in 1904, 
found the pest in Egypt, and in Asiatic Turkey at Beirut and Jeru- 
salem. Argentina was reported infested in 1905. Between 1909 
and 1914 it was found in the eastern and western parts of Africa, 
and in 1915 it was fhst reported from the Island of Madagascar. 
During 1916 it caused serious damage to the orange, tangerine, 
peach, pear, and apple crops of the Patras considar district of Greece. 
It is claimed that this was the first time in 10 years or more that this 
pest had been noticed in this district of Greece. The Bermuda 
Islands became infested during 1865. 



THE MEDITERRANEAN FRITTT FLY. 3 

ESTABLISHMENT AND SPREAD IN HAWAII. 

The presence of the Mediterranean fruit fly in the Hawaiian Ishmds 
was first discovered at Honolulu on June 21, 1910, and by the fall 
of that year the pest was weU estabhshed in the Punchbowl district 
of the city. By October, 1911, it was found on the Island of Kauai, 
and by January, 1912, on the Island of Molokai and in the Kohala 
district of the Island of Hawaii (see fig. 3). During March, 1912, 




Fig. 2.— Longitudinal sectioa of grapefruit showing destruction of pulp caused by larvw of Mediterranean 

fruit fly. (Original.) 

the Kona district was found infested, and by May of the same year 
the fruit fly was discovered for the first time on the Island of Maui. 
The towns of Naalehu and Hilea of the Kau district of Hawaii were 
infested by March, 1913, and by the early months of 1914 infesta- 
tions were found in the Hilo and the Hammakua districts of the same 
island. By July, 1914, or four years after its first discovery at Hon- 
lulu, the pest had spread to every important island of the Territory 
of Hawaii and to-day is weU established in every village and wild 
guava scrub. 



4 BULLETIN G40, IT. S. DEPARTMENT OF ACRICULTUEE. 

HOW THE FRUIT FLY GOT INTO HAWAH. 

A number of popular accounts tell how the Mediterranean fruit 
fl}^ became established in Honolulu, but thej are without foundation. 




Establisliment came as a natui'al sequence of the development of 
rapid ocean travel and cold storage, aided by unusually favorable 
shore conditions about the harbor of Honolulu. Hawaii was in no 
danger of infestation until 1S98. Before that year ships toucliing 



THE MEDTTERRAISrEAN ERUTT ELY. 5 

at Honolulu plied between countries not infested by this pest. East- 
ern Australia was not infested before 1898. With the development 
of rapid ocean transportation and cold storage on ships, the Medi- 
terranean countries were enabled profitably to export oranges to 
Australia, and it was in these shipments of fruits that the fruit fly 
reached Australian shores and became estal)lished about Perth and 
Sydney. 

Establishment in Hawaii at Honolidu followed natm'ally the com- 
mercial jump of the pest from the Mediterranean countries to Aus- 
tralia. Honolulu is a port of call for ships plying between eastern 
Australian ports and San Francisco and Vancouver, and the voyage 
of about two weeks required for passage from Australia to Honolulu 
is through a tropical climate permitting rapid development of the 
fruit fly. No one ever will know just how the pest reached Honolulu 
on these vessels from Australia, but in view of the rigid inspection 
service of the Hawaiian Board of Agricultm^e it seems probable that 
larvae falling from infested fruits in the ships' stores — in those days 
often kept on deck^ — transformed to the winged adult stage by the 
time of arrival at Honolulu. From 7 to 10 years ago trees bearing 
fruits in which the fruit fly could develop grew in greater abundance 
within a stone's throw of the docks than at the present time and 
offered an excellent breeding place for stray adults flying from the 
.ships during the time these were in port. There is probably no 
port in the world where conditions were so favorable for the estab- 
lishment of this particular pest as was that of Honolulu 10 years ago. 

LOSSES INCURRED THROUGH THE FRUIT FLY. 

The economic importance of the Mediterranean fruit fly as a pest 
of fruits varies with the climate of its natm*al abode, or habitat. 
Thus, in France, near Paris, where it has been known to attack 
apricots and peaches, it has not become a serious pest, because of 
climatic checks. Such checks to the severity of its attacks have been 
noted in portions of Australia, South Africa, and elsewhere, and 
would be operative in continental United States except in portions 
of California and the Southern States. On the other hand, in tropical 
and semitropical comitries the fruit fly is capable of becoming a pest 
of first importance, and, as in the Hawaiian Islands, may be classed 
as the most important insect pest to horticultural development. 

Practically every fruit crop of value to man is subject to attack by 
this fruit fly. Not only is it of importance as a destroyer of fruit, 
but it is the cause of numerous stringent quarantines which cost 
the State and Federal Govermnents much money to make effective 
and which rob countries of good or prospective markets for their 
fruit. Fortunately, it has been found that the Chinese banana and 
the pineapple, the two most valuable species of fresh fruits formerly 



6 



BULLETIN 640, V. S. DEPARTMENT OP AGRICULTURE. 



exported from Hawaii, offer so little danger as carriers of the Med- 
iterranean fruit fly, when they are packed for shipment, that this 
part of Hawaii's export trade in fresh fruits with the coast may still 
be carried on, provided the inspections of the Federal Horticultiu-al 

Board now in force 
are continued. The 
necessary quaran- 
tines against all other 
host fruits, however, 
particularly against 
such fruits as the avo- 
cado and mango, has 
had, and will continue 
to have, a serious ef- 
fect upon horticul- 
tural pursuits and the 
development of the 
small farmer. 

At present the in- 
festation of edible 
fruits in the coastal 
regions of Hawaii is 
general and about as 
severe as could be ex- 
pected. The work of 
the Mediterranean 
fruit fly, with that of 
the melon fly, has put 
a most serious check 
upon the horticul- 
tural development of 
the islands just at a 
time when this devel- 
opment was gather- 
ing strength. In 
South Africa the 
Mediterranean fruit 
fly is regarded as one 
of the greatest draw- 
backs to the develop- 
ment of the fruit in- 
dustry in Cape Colony, where, it is stated, during certain favorable sea- 
sons large areas of apricots, figs, pears, plums, apples (fig. 4), and 
quinces are almost all affected. Many instances of damage to citrus 
and other crops in southern Europe, South America, Africa, and Aus- 




FiG. 4.— Apples destroyed by larvfe of Mediterranean fruit fly. Al- 
though an apple externally may appear normal aside from tlie dark 
spots where the female fly punctured the skin in laying her eggs, the 
pulp is often found badly decayed and eaten out Tiy the maggots, 
as shown in the lower fruit. (Original. ) 



THE MEDITEEEANEAN FRUIT FLY. 




tralia might be added to impress one unfamiliar with the ravages of this 
pest that it is one that can not be trifled with. The amount of 
damage which would result through the introduction of this fruit 
fly is so great that every effort should be taken to prevent its estab- 
lishment in new terri- 
tory. 

WHAT THE MEDITERRA- 
NEAN FRUIT FLY IS 
LIKE. 

The adults.— The 

Mediterranean fruit fly 

is an insect that in the 

adult stage resembles in 

size and general shape 

the ordinary house fly, 

but differs greatly in the 

color pattern of the 

body and %vings and in 

its habits. In figm-e 5 

three adults may be seen 

attempting to lay eggs 

in an orange. The glis- 
tening black spots upon 

the insects' back, the 

two white bands on the yellowish abdomen, and the yellow and 

black markings of the wings at once distinguish this fruit fly from 

all other insects in Hawaii. Tlie colors, brown, yellow, black, and 

white, predominate and form a pattern that can be recognized easily 

after comparison with the drawing of the 
adult fly (fig. 1). 

The eggs. — The female fly is able to 
drill, with the sharp end of her body, small 
pinhole-like breaks or punctures in the skin 
of fruits, and through these punctures she 
lays her eggs. Naturally, these egg punc- 
tures are so small that they are not seen 
by the average pei-son. Ordinarily the fly 

^ . ^ .. , n V. . lays from one to six eggs through these 

FiG.e.— Cross section of a small apricot ^ _ • ^ t ^.^ 

showing eggs laid through skin in five holes into a Small cavity made tor them 
places. (Authors' illustration.) .^^^^ beneath in the pulp or rind. In 

some instances several hundred of the smaU white eggs, which 
are only about one-twenty-seventh of an inch long and shaped as 
those iUustratcMl in figures 6, 7, and 21, may accmnulate hi a single 
103876°— IS— Bull. 640 2 



Fig. 5.— Three adults of the Mediterraijean fruit fly on a sweet 
orange. About two-thirds natural size. (Authors' illustration.) 




8 



BULLETIN 640, U. S. DEPARTMENT OF AGEICULTURE. 




egg cavity as the result of repeated egg laying by many females 

through the same opening in the skin. 

The larvse. — The eggs hatch into whitish lai'vse, or maggots, that 

burrow or tunnel in all directions through the pulp, feeding as they 

go and causing decays to start. 
When first hatched they are very 
difficult to detect, but when full 
grown they are very white and, 
although only four-sixteenths to 
five-sixteenths of an inch long, 
are quite easily seen. Full-gro^wii 
maggots have the peculiar habit, if 
taken out of the fruit and placed 
upon a smooth surface, of curling 
up and jiunping from 1 to 6 inches. 
For tlie general appearance of 
the larvsB see figures 8 and 9, a. 

The pupsR. — After leaving the 
fruit upon which they have fed, 
the larvge either burrow into the 
soil to depths varying up to 2 

inches or seek shelter under any object upon the ground and there 

transform to the pupa or chrysalis stage. During this stage the 

insect is not al^P to move and re- 
sembles the seedlike object ifiustrated 

in figure 9, h. Although outwardly 

appearing quite dead, inwardly the 

wonderful changes are taking place 

by means of which nature transforms 

the ugly maggot into the beautiful fly; 

and in the course of a few days the 

adult fly breaks forth from the pupa, 

pushes her way up through the soil, 

and, as the mother of a second gen- 
eration, flies back to the tree and 

searches for fruits in which to lay her 

eggs. 

INTERESTING FACTS ABOUT THE ADULT FLY. 



Fig. 7.— Cross section of peach showing general 
shriveling of walls of egg ca^^ty and separation 
of eggs. Drawing made one and one-half days 
after eggs were laid. (Authors' illustration.) 




Incapable of infhcting bodily injmy 
on man, the adult fly is, nevertheless, 
the fruit growers' most persistent 
enemy in Hawaii, for she is contin- 
uously searching for fruits in which 
to lay her eggs. Adults die within tliree to four days if tliey liave 



Fig. 8.— Smallmango fruit cut to show white 
larvfe or maggots of Mediterranean fruit 
fly and damage they have caused. 
(Sevenn.) 



THE MEDITERRANEAN FRUIT FLY. 9 

no food; but if they can secure the juices of fruits or the honeydew 
of insects, which form the bulk of their food, they may live long 
periods. Two flies lived for 230 and 315 days, respectively. But as a 
rule life is much shorter, although many live to be four to six months 
old. Many die when they are very young, even if they have had food. 
In Honolulu females begin to lay eggs when 4 to 10 days old, 
and, like hens, only much more faithfully, continue to develop and 
lay eggs in fruits almost daily so long as they live. A female may 
lay on an average from 4 to 6 eggs a day, 22 eggs being the largest 
number known to have been laid by a fly during any one day. On 10 
consecutive days one fly laid 8, 11, 9, 6, 8, 3, 3, 3, 3, and 9 eggs; 
another laid 0, 5, 14, 8, 13, 10, 6, 4, 4, and eggs. The largest 
number of eggs laid during life by a single female kept in the labo- 




FiG 9.— Mediterranean fruit fly: a, Larvae, or maggots; b, pupae, or chrysalids. Twice naturalsize. 

(Original.) 

ratory was 622. This fly lived only 153 days. It is probable that 
800 eggs, or even more, may be laid by single hardy females under 
favorable conditions. 

It is also important, from the standpoint of control, to know that 
females deprived of a chance to lay eggs in fruits for a period of four 
to six months when certain crops are not in season have the power 
to begin depositing eggs as actively as younger flies when fruits 
sufficiently ripe become available for oviposition. Tlius one female 
kept in the laboratory for the first five months of her life without 
fruits in which to lay eggs laid 11, 4, 9, and 9 eggs during the first 
four days of the sixth month of her life when fruits were placed in 
the cage with her. 

CLIMATIC CONDITIONS FAVORING RAPID INCREASE IN HAWAII. 

The time recpiired by the fly to pass through the egg, larva, and 
pupa stages depends very much upon the climate. The climate of 
Honolulu and of the coastwise regions of Hawaii in general is very 



10 



BULLETIN 640. U. S. DEPAETMENT OF AGRICULTURE. 



favorable to fruit-fly increase. At Honolulu the temperature rarely 
drops as low as 58° F., and then only for a few hours during one or 

two nights in the year. 




The daily range in 
temperature is small, 
averaging between 8 
and 11 degrees, while 
the normal monthly 
m e a n temperatures 
range between 70.9° F. 
in the winter and 79° 
F. in the summer. 
Biological work has 
shown that even the 
lowest monthly means 
of localities up to 1,500 
feet elevation have lit- 
tle effect upon the fruit 
fly other than to retard 
somewhat its develop- 
ment. It is never cold 
enough tlu"oughout the 
coastal regions of Ha- 
waii to render either 
the adults or the larvae 
inactive. There are 
no periods of the year 
at any Hawaiian port 
when climatic condi- 
tions are unfavorable 
for fruit-fly increase. 
A continuous temper- 
ature of 58° to 62° F., 
or the lowest range of 
temperature usually 
experienced, does not 
increase the normal 
mortality among the 
larvae. 

LENGTH OF TIME REQUIRED 
FOR DEVELOPMENT. 

During the warmest 

Fig. 10.— Three important edilMcfrnits subject to fruit-fly attack: jj o i i mi wpntlipv 

a, Strawberry giiava; 6, loqnat; c, star apple. These are grown also Xia\V ail d 11 \\eai.liei, 
for their ornamental value. (Original.) whcU the mean tem- 

perature averages about 79.5° F., the Mediterranean fruit fly requires 
as few as 17 or as many as 33 days to pass tlu'oughits immature stages. 



THE MEDITERRANEAN FRTTTT FLY. 11 

At this season by far the hirger lunuber ])ass through these stages 
in 18 to 20 days. At an average mean temperature of 68° F., which 
is about the coolest temperature in Hawaii where fruits are gener- 
ally grown, the immature stages require 40 to 69 days. 

Just what the length of the immature stages may be in cooler 
regions can not be definitely stated, but experiments indicate that it 
may be considerably increased. The egg stage has been increased 
from a normal of 2 days at Honolulu in summer to 25 days by the 
appHcation for 22 days of a temperature of 48° to 53° F. A well- 
grown larva survived a temperature of 48° to 54° F. for 79 days. 
A newly-hatched larva remained practically dormant for 57 days at 
an out-of-door temperature ranging from 27° to 73° F. (mean 48° 
F.), whereas in Honolulu during summer it would have remained in 
this stage only 2 days. The fruit fly has been held in the pupa 
stage for about two months at an out-of-door temperature ranging 
between 38° and 72° F. (mean, about 54° F.). Had the mean been 
about 79° F., it would have remained in the pupa stage only 9 to 11 
days, Tliree larvge in very fu-m apples required 28, 58, and 74 days 
to become full grown and leave the fruit to pupate at Kealakekua, 
where the temperature ranged between 58° and 80° F. (mean, about 
68° F.). Add to the 74 days required for larval maturity 4 days 
for the egg stage and 20 days for the pupa stage, and one has 98 
days, or over three months, as the time required for the fly to pass 
through the immature stages under certain host conditions at a 
mean of 68° F. Thus while these stages may be completed in as 
few as 17 days, three to four months is a very conservative estimate 
for possible length under less favorable climatic conditions, or a 
period sufficiently long to outlast the coolest seasons of the 
semitropics. 

FRUITS, NUTS, AND VEGETABLES ATTACKED. 

The Mediterranean fruit fly is particularly injurious because it 
attacks so many more different kinds of fruits of value to man than 
does any other known fruit fly. In the Hawaiian Islands 72 kinds 
of fruits have been found infested. Fortunately, the pineapple is 
not infested, and the banana is free from attack when shipped under 
commercial conditions. The fruit fly has been reared from the 
following fruits: Fruits that are heavily or generally infested are 
marked (1), those that serve quite often as hosts or of which many 
escape infestation are marked (2), and those rarely infested are 
marked (3). 



12 BULTETTISr 640, TT, S. DEPARTMENT OF AGRTCULTUBE. 

List of host fruits of the Mediterranean fruit fly . 

SCIENTIFIC NAME. COMMON NAME. 

1. Achras sapota (3) Sapodilla. 

2. Acordia sp. (3) Acordia. 

3. Anona muricata (2) Sour sop. 

4. Arengia saccharifera (3) Sugar palm. 

5. Artocarpus incisa (3) Breadfruit. 

6. Averrhoa carambola (2) Carambola. 

7. Calophyllum inophyllnm (I) Ball kamaiii. 

8. Capsicum sp. (2) Bell peppera (fip;. 17, p. 19). 

9. Carica papaya (2) Papaya. 

10. Carica quercifolia (2) Dwarf papaya. 

11. Carissa arduina (2) Oarissa (fig. 11, //) . 

12. Casimiroa edulis (1) Sapota. 

13. Cestrum sp. (3) Cliinese inkberry. 

14. Chrysophyllum cainito (1) Star apple (fig. 10, c). 

15. Chrysophyllum oliviforme (1) Damson plum (fig. 11, d). 

16. Chrysophyllum sp. (1) Chrysophyllum. 

17. Citrus japonica (1) Oliinese orange (fig. 18, p. 20). 

18. Citrus japonica (1) Kumquat. 

19. Citrus nobilis (1) Tangerine. 

20. Citrus nobilis (1) Mandarin. 

21. Citrus medica limetta (1 ) Lime. 

22. Citrus medica limonum ( 1) Lemon (fig. 19, p. 21). 

23. Citrus decummia (1) Grapefruit (figs. 2, 20, 21 , 22, pp. 

and 23). 

24. Citrus decumana (1) Shaddock. 

25. Citrus aurantium (1) Sweet orange. 

26. Citrus aurantium var. aniara 1 1' Sour orange. 

27. Clausula wampi (3) Wampi. 

28. Coffea arabica (l) Coffee (fig. 11, h). 

29. Coffca liberica (1) Liberian coffee. 

30. Cydonia vulgaris (1) Quince. 

31 . Diospyros decandra (1) Persimmon. 

32. Eriobotrya japonica (1) Loquat (fig. 10, b). 

33. Eugenia brasiliensis (1) Brazilian plum or Spanish cherry, 

34. Eugenia jambos (1) Rose apple (fig. 11, g). 

35. Eugenia michelii (1) Surinam cherry. 

36. Eugenia uniflora (1) French cherry. 

37. Ficus carica (1) Fig. 

38. Garcinia viangostana (2) Mangosteen. 

39. Garcinia xanthochymus (2) Mangosteen. 

40. Gossypium spp. (2) Cultivated cotton (fig. 11, e] 

41. Jambosa malaccensis (2) Mountain apple. 

42. Lantanis placuachuUa (3) Palm. 

43. Lycopersicum esculentum (2) Tomato. 

44. Litchi chinensis (3) Lichee nuts (fig. 11, c). 

45. Mangifera indica (1) Mango (figs. 8, 24, pp. 8 and 25). 

46. Mimusops elengi (1) Elengi tree (fig. 11, i). 

47. Murraya exotica (1) Mock orange (fig. 11, /). 

48. Musa spp. (3) .Banana (figs. 14 and 15, p. 17). 

49. Noronhia emarginata (3) Noronhia. 

50. Ochrosia elliptica (2) Ochrosia. 



THE MEDITERRANEAN- FRUIT FLY. 




Showing drops of white sap that exurXVthf fl™cf L^^ 'f • '"; '''' ^""* "-^■■- "' '^'^^ ^««"^1' 
show the maggots feeding on the pu^p c the lichee m^H^nf .. f ^^°,' ''' ^ '°'^'' ''^'^"'y «<'''"°'^^d to 
ha^ broken; d, a damson plum, showLl^ adu^ A v -, .,? ^"'^'^'^'^'^/'J' ^he fly unless the outer skin 
by the pink bollworm and the fruSy Ta dulr ofTnfi '° *^' f '""^ '^P- ^' ^ ^°"°° '^"'l i'^ested 
showfruit-fly attack; h, thecmssa shLfn^Hrn. !'f '"o^k-orange berries; ;?, arose apple sectioned to 

intheskinbythefrt;itfly;X:ieSrSittK^^^^^^^^ 



14 BULLETIN G40, TT. S. DEPARTMENT OP AGRICULTURE. 

51. Opuniia vulgaris (2) Prickly ])ear. 

52. Passiflom sp. (3) Passion vine. 

53. Fersea gralissima (2) Avocado (fig. 13). 

54. Phoenix dactylifera (3) Date palm. 

55. Psidium cattleyanum (1) Strawberry guava (fig. 10, a). 

56. Psidium guayava (I) Sweet red and white lemon guuvaa. 

57. Psidium guayava pomifemm ( 1 ) Common guava. 

58. Psidium guayava pyriferum (3) Waiawi. 

59. Prunus persica (1) Peach (fig. 7, p. 8). 

60. Prunus persica var. nectarina ( L ) Nectarine. 

61. Prunus armeniaca (1) Apricot (fig. 6, p. 7). 

62. Prunus spp. (1) Plum. 

63. Punica granatum (3) Pomegranate. 

64. Pyrus spp. (1) Apple (fig. 4, p. G). 

65. Pyrus spp. (1) Pear (fig. 12). 

66. Solanum melongena (3 ) Eggplant. 

67. Spondias dulcis (3) Wi. 

68. Terminalia catappa (I) Winged kamani or tropical almond. 

69. Terminalia chebula (L) Natal plum. 

70. Thevetia nerii/olia (1) Bestill (fig. 11, a). 

71. Vitis labrusca (3) Grape (fig. 25, p. 26). 

72. SantalUm freycinetianum var. littorale 

(3) Beach sandalwood. 

This list shows that practically all the ordinary useful and edible 
fruits in Hawaii are hifested heavily. Thus peaches can not be grown 
at present, for they are ruined before they become well grown; Chi- 
nese oranges (fig. 18), tangerines, figs, loquats (fig. 10, I), rose apples 
(fig. 11, ^),many varieties of mangoes (figs. 8, 24), certain avocados 
(fig. 13), guavas (fig. 10, a), coffee cherries (fig. 11, h), star apples 
(fig. 10, c), sapotas, persimmons, apples (fig. 4), pears (fig. 12), 
plums, nectarines, and quinces — all these are badly infested. On the 
other hand, a large percentage of the ripenhig fruits of the tomato, 
prickly pear, mangosteens, mountain apples, and wampis are free 
from attack, although certain fruits may be at times heavily infested. 
When tomatoes are wormy, the melon fly, and not the Mediterra- 
nean fruit fly, is usually tlie insect doing the damage. Ordinarily, 
sweet bell peppers are not generally infested, and cotton bolls be- 
come infested only after they hav(> been damaged by some other 
insect (figs. 17 and 11, e). 

The pomegranate, breadfruit, eggplant, wi, grape (fig. 25), date, 
certain seeds of pahns, lichee nuts (fig. 11, c), and the Chinese ink- 
berry are very rarely infested, even in Honolulu. For practical pur- 
poses they may be said to be immmie. Lichee nuts ripening on the 
tree become infested only when the outer shell breaks, thus exposing 
the white pulp to attack. 

Hawaiian iruits, nuts, an<l vegetal)l(>s not listed are free from 
attack. 



THE MEDITERKANEAN FEUIT FLY. 



15 



ORNAMENTALS SERVING AS HOSTS. 

Not only does the Mediterranean fruit fly attack the ordinary 
cultivated fruits, hut in Hawaii it has shown a preference for the fruits 
of many ornamental trees and shruhs. Thus the nuts of the winged 
kamanijtha ball kama- 
ni, the rose apple, dam- 
son plum, star apple, 
Brazilian plum or Span- 
ish cherry, the Surinam 
and French cherries, 
the berries of the mock 
orange and elengi tree, 
the fruits of the Natal 
plum, and the mature 
fruits of the bestill are 
allusually well infested . 
Even the fruits of cer- 
tain palms and the 
beach sandalwood may 
harbor the fly. Orna- 
mentals less subject to 
attack may be found in 
the foregoing complete 
list. 

HOST FRUITS OF COM- 
MERCIAL VALUE. 

PINEAPPLES. 

Many experiments 
have been carried on to 
determine whether the 
Mediterranean fruit fly 
can live in the pineap- 
ple. It has been found 
that even under forced 
laboratory conditions 
the fly can not live or 
mature in green or ripe pineapples. No person has ever found a 
pineapple infested by this pest in Hawaii. 

PAPAYAS. 

The papaya is one of the commonest plants about Honolulu. Its 

fruit is the universal breakfast fruit. Probably not one person in a 

thousand in Honolulu, however, knows that papayas become infested. 

Unless the fruits are allowed to remain upon the trees until overripe, 

103876°— 18— Bull. 640 3 




Fig. 12.— Bartlett pear, the pulp of which has heen entirely eaten 
out by the maggots of Ihe Mediterranean fruit fly. The fruits 
often remain on the tree and shrivel up after they have been 

ruined. (Authors' illustration.) 



16 



BULLETIN 640, U. S. DEPARTMENT OF AGRICULTUEE. 



the fruit fly can not mature in them. The milky juice, which exudes 
copiously from breaks in the skin of the fruits up to the time when 

the fruits can be cut 
for ripening in tlie 
house, contains a di- 
gestive principle that 
is fatal to the eggs 
and larvae of the fly. 
This juice protects 
the fruits from infes- 
tation when imma- 
ture. But as the 
fruits become over- 
ripe, and also unfit 
for the table, the juice 
flows less abundantly 
from breaks in the 
skin made by the fly 
when she attempts to 
lay her eggs, and the 
eggs which she then 
lays can mature. As 
many as 205 fhes have 
been reared from sin- 
gle overripe fruits. 
So while the papaya 
is a host fruit, it is 
practically never in- 
fested until too ripe 
or otherwise unfit for 
the table. 

AVOCADOS. 

With the exception 
of one or two early 
varieties, the infesta- 
tion of the avocado 
is so obsciu"e that the 
general belief prevails 
in Honolulu that this 
fruit is free from at- 
tack. The Guate- 
mala, or nutmeg, variety is the only one free from attack when growing 
uninjured. Theskinof allother varieties, whether tliinorof usual tough- 
ness, can be punctured by the adult fly, as proved by many examinations 
of fruits. The avocado, hke the ordinary pear, is best when picked 




Fig. 13.— Avocado. This valuable fruit of California and Florida is 
subject to infestation in Hawaii. In this instance the maggots are 
working at the stem and blossom ends. (Authors' illustration.) 



THE MEDITEERANEAlSr FRUIT FLY. 



17 




Fig. 14. — Cooking banana of the Popoulu variety taken from tree in an infested condition. Note small 
round holes in the skin through which maggots left the fruit when they became full grown. (Authors' 
illustration.) 




Fig. 15.— Cooking banana of the Moa variety cut to show destruction of pulp by maggots of the Medi 
terranean fruit fly. (Authors' illustration.) 



18 



BULLETIlSr 640, U. S. DEPARTMENT OF AGRICULTURE. 



while still hard, though mature, and allowed to soften in storage. 
With most varieties it is not until the fruits are mature enough for 
gathering or dropping that adults lay eggs in them. Many fruits 
upon the market are not in the least affected. While avocadoes are 
not usually a favorite host for the fly, they are sufficiently infested 
to warrant the quarantine prohibiting the sliipment of them to the 
mainland. (See fig. 13.) 

BANANAS. 

Experimentation during the past four years in Hawaii has proved 
that the Chinese banana ^ and the Bluefields banana ^ are prac- 
tically immune from attack if harvested and shipped to the coast in 
accordance Anth the demands of the trade and the Federal Horti- 




FiG. 16. — Loss to coffee-mill owners due to infestation of coffee cherries by Mediterranean fruit fly. 
Coffee beans to left pulped from uninfested cherries; beans to right pulped from infested cherries. 
Cherries failing to pulp, because infested, appear as black; pulped beans are grayish white. (Orig- 
inal.) 

cultural Board. Persons wishing the results of careful experimental 
work used as a basis for these conclusions may obtain them in 
printed form by applying to the Bureau of Entomology. The 
immunity of commercial varieties of bananas has been shown to be 
due to the fact that neither the eggs nor the newly-hatched larvae 
can survive in the tamiin-laden peel of the green though mature fruit. 
Indeed, the copious and sudden flow of sap from egg punctures made 
by the female fly in unripe bananas renders the successful placing of 
eggs in such fruits difficult and rare. 

No fruits of the Cliinese variety ripening prematurely on bunches 
in plantations have been found infested. But of the cooking bananas, 
flies have been reared from the ripe and yellomsh fruits of the thin- 
skinned Popoulu variety (fig. 14) growing in the field, and from the 



1 Musa cavendishii. 



2 Musa sapientum. 



THE MEDITEEBANEAN FRUIT FLY. 



19 



well-grown though green-colored fruits of the Moa variety, the peel 
of which had become cracked, thus causing a break in nature's normal 
protection to the pidp. Figure 15 is a cross section of a Moa banana, 
showing the tunnels made through the pulp by the laiTse, and the 
darkened decayed areas about the tumiels. Adults have been reared 
also from another variety of cooking bananas. 

Because flies have been reared from cooking bananas, it is not 
considered safe to permit their export to the coast, and they have 
been placed on the 
list of quarantined 
fruits by the Federal 
Horticultural Board. 
The Chinese and Blue- 
fields bananas may 
still be exported from 
Hawaii, provided 
they are grown and 
inspected before slii]>- 
ment in accordance 
with Federal regida- 
tions. So far as is 
known, the "apple" 
and the ''ice-cream" 
bananas common in 
Hawaii are not in- 
fested. 

COFFEE. 

Coffee cherries as 
they ripen are favor- 
ite hosts of the Medi- 
terranean fruit fly. 
Fortunately, the 
larvfe attack only the 
pulp surrounding the 
beans or seeds, and 
in no way affect the 
value of the latter (see 
fig. 11, h). Chemical analyses of beans from infested and uninfested 
cherries, tasting tests of coffee made from similar roasted beans, and 
weighings made of dried beans have failed to reveal any iU effect to 
the beans themselves due to fruit-fly attack. 

The unrestricted development of larvae within coffee cherries, 
however, does bring about certain losses to the grower and mill 
owner. Before parasites were introduced cherries became infested 




Fig. 17.— Sweet bell pepper infested by Mediterranean fruit-fly larvae. 
Note that the upper right-hand portion of fruit has decayed as a 
result of attack. This decay later extends to all parts of the fruit. 
(Original.) 



20 



BULLETIN 640, U. S. DEPAETMEZSTT OF AGRICULTTJEE. 



as soon as they began to turn white from green m the final ripening 
process, and the larvae, numbering from 2 to 8, were able to become 
nearly full grown by the time the cherries had turned red. The pulp 
surrounding the beans varies from two to seven fifteenths of an inch 
in thickness, or is scarcely thicker than the well-gro^vn larva of the 
fruit fly (see fig. 30, p. 39), Therefore, by the time the cherry is ordi- 
narily ready for harvesting, the larvae have devoured practically all 
the pulp, leaving the seeds hanging more or less loosely within a 
sack comprised of the thin skin of the cherry. If the weather 
happens to be dry, the skin shrivels and hardens about the beans 

and the cherry remains on 
the branch indefinitely and 
resembles those killed by 
disease. However, should 
the harvesting season be 
rainy, the skin decays rap- 
idly, and under the weight 
of the beans the cherry falls 
to the ground. A slight j ar 
may at such times cause 
many cherries to fall to the 
ground, where they are 
lost. This type of loss ne- 
cessitates extra pickings 
and greater cost for labor. 
Since the successful intro- 
duction of parasites the 
fruit fly has been so re- 
duced in the coffee field 
that the infestation of 
cherries occurs so late in the ripening process that extra pickings 
are not necessary, and the cherries on reaching the pulping mills 
during the height of the harvesting season contain chiefly eggs 
or young larvae which have not had an opportunity to reduce the 
pulp. 

Badly infested cherries do not pulp as readily when rmi tlirough 
the pulping mill, and natiu-ally weigh much less than sound cherries. 
(Fig. 16.) The loss in number of chemes in a given weight of badly 
infested fruit has been found to vary at times from 27 to 59 per cent. 
This loss in weight, which takes place only in the worthless pulp, and 
in no way affects the bean, which alone is of commercial value, 
brought about a financial loss to growers who sold their fruit by 
weight according to prices obtained before the fruit fly was intro- 




FiG. 18.— Chinese orange sectioned to shoT/ damage by Medi- 
terranean fruit fly. Chinese oranges, Ivumquats, tanger- 
ines, satsuma oranges, and many limes are easily and gen- 
erally infested because of their loose peel and lack of a thick 
protective rag. (Original.) 



THE MEDITEEEANEAN FEUIT FLY. 



21 



duced. This has been appreciated and has caused a readjustment of 
prices paid for coffee "in the cherry'' and has been responsible for 
the erection of many small pulping mills throughout the Kona coffee 

district. 

It seems reasonable to believe that the remarkable success of 
introduced parasites in checking the infestation of coffee will free the 
coffee grower from fur- 
ther worry so far as the 
Mediterranean fruit fly 
is concerned. 



'^■^PW^- 






CITRUS FRUITS. 

While all citrus fruits 
are favorite hosts of the 
Mediterranean fruit fly, 
certain of them are 
found to contain larvae 
more often than others. 
No citrus fruits are too 
acid for fruit-fly devel- 
opment. Larvfe have 
been reared from the 
som-est lemons. Adult 
flies are fond of laying 
eggs in large numbers 
in all citrus fruits. Thus 
13 punctures in one 
grapefruit contained 
76, 153, 32, 25, 18, 8, 
46, 113, and 9 eggs, re- 
spectively. Thirty-nine 
oranges, either yellow 
or orange in color, con- 
tained an average of 32 
egg punctures, with a 
maximum of 108 and a minimum of 7 punctures. In 50 ripe lemons 
1,422 eggs were laid in 185 punctm-es. Yet no adult flies developed 
from this grapefruit or from the oranges and lemons. On the other 
hand, well ripened Chinese oranges (fig. 18), thin-skinned limes, kum- 
quats, and tangerines are so generally infested with larvae in the 
pulp before they become well ripened that they are always regarded 
with suspicion. 

Although many eggs are laid in lemons, it is rare that lemons 
are found with maggots in the pulp even when the fruits are so ripo 




Fig. 19. — Lemons of commercial varieties have never been foimd 
with larvce of the Mediterranean fruit fly destroying the pulp 
unless they have had the rind cut or broken previous to attack. 
The adult flies may puncture the skin and lay eggs, as indicated 
by the discolored spots, but the eggs and larvae die in the peel. 
(Original.) 



22 



BULL?:TIX 640, U. S. DEPARTMENT OF AGRICULTURE. 




Fig. 20.— Ripe grapefruit showing copious gummy secretions that 
may, though more often do not, follow attack bv Mediterranean fruit 
fly. (Original.) 



that they fall to the 
ground. Why, then, 
are Chinese oranges 
and tangerines easily 
infested with larvae 
in the pulp whereas 
lemons, grapefruit, 
and oranges ward off 
fatal attack either 
entirely or until after 
they are overripe ? 

The reason is that 
a great mortahty oc- 
curs among the eggs 
and newly hatched 
larvae in citrus fruits 
having a thick peel- 
ing or rind. In Chi- 
nese oranges the peel is so thin that the fruit fly can lay her eggs 

through it into the pulp itself or between the pulp and the rind, 

so that the larvae on hatching can at once begin 

to feed on the pulp. As a result the pulp of 

the Chinese orange (fig. 18) is almost always 

infested with larvae. The case is different with 

lemons (fig. 19), grapefruit (fig. 20), and ordi- 
nary seedling oranges. In these fruits the peel 

is so thick that the fly must deposit her eggs in 

the outer part of the white rag as illustrated in 

figure 21. In making the punctm-e she often 

ruptiu-es an oil cell in the rind, and the oil thus 

liberated kiUs the eggs. But if the eggs are laid 

between oil cells, the young larvae have difficulty 

in making their way through the rag to the pulp, 

and a very high percentage of them die in the 

attempt. 

Then, too, a gaU-Uke hardening develops quite 

rapidly about the egg cavity in oranges, grape- "^iil -sji^ 

fruit, and lemons, as mdicated by the darkened '~ 

area about the egg cavity in figm^e 21. This 

hardenmg often makes of the cavity a prison 

from wliich the young larvae can not escape and 

in which they are literally starved to death. 
It thus happens that the larvae that succeed 

in entering the rag of the peel from the egg 

cavity are able to reach the pulp of grapefruit 




Fig. 21.— Section of grapefruit 
rind, showmg two egg ca\-i- 
ties, one in cross section. 
Drawing made one week af- 
ter fruit was picked. Note 
conical elevation aliout egg 
cavities left by withering of 
rind; also thickened walls of 
egg cavity and single larval 
channel in the rag. (Authors' 
illustration.) 



THE MEDITERRANEAN FRUIT FLY. 



23 



and oranges in astonishingly small numbers because of the imper- 
Tiousness of the rag. It is the persistent attack of successive families 
of larvae hatching from different batches of eggs laid in the same 
punctures that finally breaks down the barrier between the young 
larvae and the pulp. A fuller discussion of the infestation of all citrus 
fruits may be had on appHcation to the Bureau of Entomology. 

Regardless of what has just been stated concerning the great 
mortality that occurs among the eggs and young larvae in the rind 




Fig. 22.— Cross section of grapefruit to indicate difficulty of always telling from exterior appearance of a 
fruit that maggots are eating out the pulp. (Authors' illustration.) 

of grapefruit, oranges, and lemons, adult flies have been reared from 
them all. Lemons, however, have never been known to be infested 
in the pulp unless the rind has first become broken by thorn pricks, 
decays, or in some other mechanical manner. And in spite of the 
fact that oranges and grapefruit may become very wormy, as illus- 
trated in figm-es 2 and 22, they are usually uninfested in the pulp, 
and are fit for table use if they are gathered as soon as they ripen. 
But if citrus fruits were grown commercially in Hawaii in large 



24 



BULLETIN 640, U. S. DEPARTMENT OF AGEICULTUEE. 



orchards as they are in Florida and Cahfornia, and were severely 
attacked as they are in Hawaii to-day, they could not be shipped 
profitably, for, although they might not contain larvse within the 
pulp, the many breaks in the rind made by the flies while laying eggs 
would make possible the entry of various molds (see fig. 23) that 




Fig. 23.— Orange injured by Mediterranean fruit fly. Each black spot represents a place where the fruit 
fly has punctured the rind to lay eggs, but the maggots were not able to eat through the peel, and died. 
About the injured spot decays have started which at first afiect only the peel. Blue mold grows rapidly 
in these injured spots. (Original.) 

would cause unprecedented decays while the shipments were en route 
to market. 

ARTIFICIAL METHODS OF CONTROL NOT SATISFACTORY UNDER 
HAWAIIAN CONDITIONS. 

It is mifortunate that the satisfactory methods of control used 
agamst the Mediterranean fruit fly in several other countries, par- 
ticularly m portions of South Africa and Australia, have failed in 
Hawaii. There are, however, several good reasons for such failures. 
The great money-making crops of Hawaii at present are sugar, pine- 
apples, rice, coffee, taro, bananas, and cattle. But sugar, pmeapples, 
and taro are not attacked by this fruit fly, and, as already showni, 
coffee and bananas are not sufficiently attacked to injure their com- 
mercial value. With one exception, including a small number of 



THE MEDITEEKANEAN FRUIT FLY. 



25 



avocados, no commercial orchards exist in Hawaii. StiU there is 
hardly a family, unless it be in the business section of Honolulu, 
that does not grow a number of fruit trees, such as oranges, lemons, 
papayas, peaches, avocados, limes, grapefruit, guavas, bananas, man- 
goes, etc., that bear prodigally under normal Hawaiian cultural con- 
ditions, and, until the advent of the fruit fly in 1910, fonned a most 
welcome addition to the food supply. 

Much of the native-grown fruit that is sold in the local market is 
grown on trees scattered here and there in dooryards and is in 
excess of what the 
owner needs. Practi- 
cally no one depends 
on growing fruit for 
his livmg. No devel- 
oped fruit industry 
exists such as one 
finds on the main- 
land, and no moneyed 
interest concerns it- 
self with steps for 
fruit-fly eradication. 
In other words, there 
are no impelling in- 
centives to solidify 
public opinion for the 
consistent and coop- 
erative use of artificial 
remedial measures 
that could be made 
effective if their ap- 
plication would yield 
returns warranting 
the expenditure. 

Tlie situation also 
is made more difficult 
by reason of the large amount of vegetation, bearmg fruits of little 
or no value to man, that grows throughout the islands and that 
can not be eradicated without the expenditure of prohibitive sums 
of money. 

But this great abundance of dooryard and wild host vegetation 
has had such a vital part in the undoing of artificial control measures 
and in the success of parasite introductions that it is worthy of fur- 
ther attention. Aided by a favorable clhnate, it has made of Hawaii 
a fruit-fly paradise that is not duplicated elsewhere on the earth. 




Fig. 24.— Improved mango sectioned to show havoc caused by maggots 
of Mediterranean fruit fly. (Authors' illustration.) 



26 BULLETIN 640, U. S. DEPARTMENT OF AGRICULTURE. 

THE CAMPAIGN AGAINST THE FRUIT FLY IN HAWAII. 

HOST CONDITIONS IN HONOLULU AND HILO. 

The residents of Honolulu and Hilo are justly proud of their mag- 
nificent vegetation and have taken great pleasure in growing an 




Fig. 25.— This Inmch of grapes, apparently perfect , eon- 
tains one lierry that is decayed and contains a iarva 
of the Mediterranean fruit fly. The Isabella grapes 
in Hawaii are seldom attacked, even in Honolulu, 
yet they are likely to carry the fly to California. 
(Original.) 

unusually large assortment of trees and shrubs on their properties. 
An inventory of such trees and shrubs in the portion of Honolulu 
bounded by Lililia, Punchbowl, Beretania, and School Streets gave 
a total of 4,610 that bore fruits in which the fruit fly can develop. 



THE MEDITEERANEAN FRUIT FLY. 



27 



Table II. — Number and species of host trees of the Mediterranean fruit fly growing 'in that 
portion of Honolulu bounded by Liliha, Punchbowl, Beretania, and School Streets. 



Apricot 

Avocado 

Breadfniit 

Carambola 

Chinese inkberry . 



1 

653 

58 

48 

6 

Chinese orange 148 

298 

8 

..-. 11 

1 

4 

20] 

94 

73 

80 

4 

13 

4 

22 

40 

10 

33 



Coffee 

Coffee, Liberian 

Cotton -. 

Custard apple 

Damson plum 

Fig 

Guava, common 

Guava, strawberry 

Java plum 

Kamani, ball 

Kamani, winged 

Kumquat 

Lemon 

Lichee 

Lime 

Loquat 33 Total 4,010 

In tliis area of 60 blocks of varying size, 712 dooryards, or estates, 
averaged 6.5 host trees or shrubs. 

In Hilo, island of Hawaii, host conditions are quite as favorable for 
fruit-fly increase as in Honolulu. Thus the following numbers of host 
trees and slirubs were found in certain yards during March, 1914. 



Mandarin 28 

Mango 1^ 154 

Mangosteen 7 

Moimtain apple 41 

Mock orange 33 

Orange, sweet 372 

Papaya 687 

Peach 

Pear, Bartlett 

Pomegranate 

Pomelo 

Rose apple 

Sapodilla 

Sapota 

Sour sop 

Spanish cherry 

Star apple 

Surinam cherry 

Wi ". 

Waiawi 



69 
2 

128 

15 

25 

5 

30 

57 

1 

4 

63 

19 

60 



Yard 1. 

Rose apple 1 

Surinam cherry 4 

Japanese plum 2 

^Mountain apple 6 

Star apple 1 

Coffee trees 34 

Common guava 20 

Brazilian banana 15 

Avocado 4 

Mango 3 

Papaya 2 

Orange 5 

Peach 1 

Grape 1 

Winged kamani 1 

Mangosteen 1 

Fig 1 

Mimusops 1 



Yard 2 — Continued. 

Orange 2 

Strawberry guava 2 

Coffee 14 

Bananas. 

Avocado 2 

Peach 1 

Fig 8 

Mountain apple 2 

Lichee nut 2 

Common guava 3 

Yard 3. 

Rose apple 11 



Mango . . . 
Thevetia. 
Avocado . 



Yard 2. 



Surinam cherry. 

Papaya 

Thevetia 



Yard 4. 

Peach 4 

Mango 6 

Loquat 1 

Winged kamani 3 

Surinam cherry 2 

Strawberry guava 1 



28 



BULLETIN 640, U. S. DEPARTMENT OF AGRICULTURE. 



The great variety of host vegetation wliich ripens its fruit at 
different seasons leaves no time in Hawaii when fruits are entirely 
out of season. The fact that certain hosts, such as the Chinese 
orange, Surinam cherry, and mock orange, bear several crops a year 
and others, such as specimens of the ball and the winged kamanis and 
the bestiU, appear to be seldom entirely free from ripening fruits, 
assure food for the fruit fly the year round. The succession of fruits 
also is increased by the individuality of trees of the same species, or 
even of certain branches of a single tree, wliich results in a very 
uneven rij^ening of the fruit. While the data in Table III do not 
indicate the seasonal abundance of host fruits, they have been sum- 
marized from the collections of clean-culture inspections during 1913 
to show the remarkable succession of host fruits ripening in greater 
or less abundance throughout the year in Honolulu. The presence of 
so much ripening fruit, much of it on tall trees such as those illustrated 
in figures 26, 27, and 28, has made it possible for the fruit fly to 
multiply with unprecedented rapidity and thwart artificial remedial 
measures. 

Table III. — Data indicating the seasons of the year when inspectors of the clean-culture 
campaign collected various fruits infested by the Mediterranean fruit fly. ^ 



Fruit. 



Avocado 

Carambola 

Chinese orange 

Chrysophyllum spp. 

Coffee 

Damson plum 

Surinam cherry 

Fig. 



Grapefruit 

Guava 

Kamani, ball 

Kumquat 

Lime 

Loquat 

Mango 

Mock orange 

Mountain apple. . 

Orange 

Papaya 

Peach 

Pepper 

Prickly pear 

Rose apple 

Star apple 

Bestill 

Soiu' sop 

Mandarin 

Lemon 

Kamani, winged . 
Spanish cherry . . 
Bartlett pear 






1 This table is not intended to indicate the seasonal abundance of host fruits. 



THE MEDITERRANEAN FRUIT FLY. 



29 



Table III. — Data indicating the seasons of the year when inspectors of the clean-culture 
campaign collected various fruits infested by the Mediterranean fruit fly ^ — C'ontinued. 



Fruit. 



Avocado 

Carambola 

Chinese orange 

Chrysophyllum spp. 

Cofiee 

Damson plum 

Surinam cherry 

rig 

Grapefruit 

Guava 

Kamani, ball 

Kumquat 

Lime 

Loquat 

Mango 

Mock orange 

Mountain apple 

Orange 

Papaya 

Peach 

Pepper 

Priclvly pear 

Rose apple 

Star apple 

Bestill 

Sour sop 

Mandarin 

Lemon 

Kamani, winged. . . . 

Spanish cherry 

Bartlettpear 



X I X 

x' X 

I 

xVx 



X 



X X 
X X 



X X 
X X 



X I X 

... X 






X X 

X X 

X X 

X .... 

X X 



X X 

X ---. 

X ..-. 

X X 

X X 

X X 

X X 



X X 



XXX 
XXX 
X 



X X 

X .... 



X X 



Fruit. 


t 


p. 


ft 


ft 


Is 


3 

o 

o 


o 

o 


1 

o 


1 . 

o O 


t 

> 
o 


«3 

1 

> 

o 


2 
> 

o 


o 

2 

o 


6 



<3> 

p 




i 


Avocado 


X 
X 
X 


X 
X 
X 
X 
X 


X 
X 
X 
X 
X 


X 
X 
X 

x' 


X 
X 
X 
X 
X 






X 
X 
X 
X 
X 












X 
X 
X 


X 
X 
X 


X 
X 
X 


V 


Carambola. . . . 


X 
X 


X 
X 


X 
X 


X 
X 


X 
X 


X 
X 


X 
X 


V 


Chinese orange 

Chrysophyllum spp 


X 


Coffee 


X 


X 


X 


X 


X 


X 


X 


X 


X 


X 


X 


Y 






Surinam cherry 


X 
X 


X 
X 


X 


X 
X 


X 

x' 

X 
X 
X 
X 


X 
X 
X 
X 
X 
X 
X 


X 


X 


X 


X 

X 
X 


X 
X 
X 


X 
X 

"x" 

X 


X 
X 
X 
X 
X 
X 
X 
X 

"x 

X 


X 
X 
X 
X 
X 
X 
X 
X 
X 
X 
X 
X 
X 


X 
X 
X 
X 
X 


X 

x" 

X 
X 


y 


Pig 


Y 


Grapefruit... 


■><■ 

X 
X 
X 


X 
X 
X 
X 
X 


X 
X 
X 
X 
X 


Y 


Guava 


X 
X 


X 
X 
X 
X 


X 
X 
X 
X 


X 
X 
X 
X 


Y 


Kamani, ball. 


Y 




Y 


Lime 




X 
X 
X 
X 
X 
X 
X 
X 
X 


X 
X 
X 
X 

"x" 

X 


X 
X 
X 
X 
X 
X 
X 


X 
X 
X 
X 


X 
X 
X 
X 


Y 


Loquat . . ' 


Y 


Mango 

Mock orange 


X 
X 










i 1 


X 
X 


Y 


X 




X 


X 


X 


X 


X 


X 
Y 




X 
X 
X 
X 
X 


X 
X 


X 
X 


X 
X 


X 
X 
X 


X 
X 


X 
X 


X 
X 


X 
X 


X 
X 


X 
X 


Y 


Papaya 


Y 




Y 




X 
X 


X 


X 
X 
X 


1 


X 
X 
X 


X 


X 


X 


X 


X 
X 


X 
X 


X 
X 
X 


Y 




X 
X 


X 


X 
X 


Y 














Y 






















X 
X 
X 
X 
X 
X 
X 




Bestill 


X 
X 
X 
X 
X 
X 


X 
X 
X 
X 
X 
X 


X 
X 
X 
X 
X 
X 


X 
X 
X 
X 
X 
X 


X 
X 
X 
X 
X 
X 


X 
X 
X 
X 
X 
X 


X 
X 
X 
X 
X 
X 


X 
X 
X 
X 
X 
X 


X 
X 
X 
X 
X 
X 


X 


X 


X 


X 
X 
X 
X 
X 


X 

x' 

X 
X 


X 

"x" 

X 
X 
X 


Y 




Y 




X 
X 
X 
X 


X 
X 
X 
X 


X 
X 
X 


Y 


Lemon 


X 


Kamani, winged .... 


X 




Y 














1 








1"'"' 


1 















30 



BULLETIN 640, U, S. DEPABTMENT OF AGEICULTUEE. 



HOST CONDITIONS IN THE COUNTRY. 

While host conditions within the city limits render useless such 
artificial control measures as can be applied under existing condi- 
tions, country host conditions are almost, if not quite, as discour- 
aging. Here the fruit fly has been able to establish itself, often 
miles from towns, in some one or more of its hosts which have es- 
caped cultivation and have spread over uncultivated and uncultiva- 
ble areas. Of such hosts, the common guava is the most abundant. 
It has taken possession of the roadsides, pastures (as shown in fig. 
26), vacant town lots, mountain gulches and hillsides, and even 
crevices on precipices. So easily does the plant grow from seed and 
so thoroughly distributed are its seeds by cattle, birds, and man, 




Fig. 26. — Men cutting down a dense thicket of guava bushes. In such a guava scrub ripening fruits are 
present throughout the entire year and in them the Mediterranean fruit fly breeds, often far from culti- 
vated fields. (Authors' illustration.) 

that it is seldom that in the lowlands, except in very arid areas, a 
bush can not be found within a stone's throw. In pastures and moun- 
tain gulches up to an elevation of at least 1,500 feet, particularly 
where sheltered from strong winds and well watered, the guavas may 
become very treelike and form dense thickets. Wliile the guava 
fiTiits most heavily during the spring and fall months, the bushes 
are continuously in bloom and ripen a sufficient number of fiiiits to 
support the fi-uit fly every month in the year. 

Second to the guava as a host occurring in the wild uncultivated 
areas is the prickly-pear cactus. Though the fruits of this plant are 
not preferred by the fruit fly, they are sufficiently infested in the 
absence of more favored hosts to serve as food, and, as in the case of 
the guava, there is almost no time during the year when a few ripe 
fruits can not be found in any cactus scrub. 



THE MEDTTET?RANKAX FTITTTT FLY. 31 

Other host fruits, wild or escaped, are not so generally distributed. 
As a few of the many examples, there may be mentioned a grove of 
ball kamani trees in an isolated valley on the Island of Molokai, 
gulches overgrown with the passion vine and the damson plum on 
the island of Maui, the thickets of winged kamani growing along the 
windward shores of the island of Oahu, and the wQd coffee in the 
forests of Oahu and Hawaii. 

In addition to the wild fniits m country places, the fruit fly finds 
strongholds in the many, and often isolated, native home sites scat- 
tered throughout the coastal region. About these may be growing 
the mango, rose apple, orange, peach, ball and winged kamanis, etc. 
The Kona district of Hawaii has large areas containing thousands of 
acres of coffee under cultivation in which the fruit fly finds food at 
all seasons of the year, because of the uneven ripening of the crops 
due to the varying altitudes at which coffee is grown. 

CLEAN CULTURE A FAILURE IN HAWAII. 

Clean culture in its broadest sense includes not only the detection, 
collection, and destruction of all infested fruits, but also the ehmi- 
nation of useless or unnecessary host vegetation. In some one or all 
of its phases it has been recommended and practiced in every coun- 
try where the fruit fly is a pest, but in nearly all of these the apparent 
indifference displayed by the majority of the people, no matter how 
much they may have lamented their losses, has rendered clean culture 
mefhcient. 

The clean-culture campaign instituted by the Hawaiian board of agri- 
culture during the fall of 1911 and continued ])y the Federal Bureau 
of Entomology from October, 1912, until April, 1914, was a failure from 
the very start in that it did not protect fniits from attack. There were 
minor contributory causes, but the main reason for failure was the 
insurmountable difficulties placed in the way of success by territorial 
legislation, adverse host and climatic conditions, and the lack of any 
commercially grown crop worth protecting. This method of control 
proved hopeless after the first few months' trial from the stand- 
point of alleviating the Hawaiian situation, and while the destruction 
of fruit was encouraged, in the absence of a better plan for lessening 
the opportunities for spread of the pest to the coast by means of 
infested fi-uits carried on board ships sailing from Honolulu, it has 
since been discontinued. 

It is doubtful if any clean-culture campaign agamst the fruit fly 
has ever been organized so efficiently or on so large a scale as was 
that organized by the Hawaiian board to mclude Honolulu. That 
this method should prove a failure under Hawaiian conditions is no 
reflection upon the ability of those directly in charge of the work. 
The law prohibited inspectors from gathering and destroying the 



32 



BULLETIN 640, U. S. DEPARTMENT OF AGETCULTUEE. 



fi-uits unless they could first prove to the satisfaction of the property 
holders that each finiit was infested. This restriction placed upon 
the activity of the inspectors led to numerous difficulties between 
inspectors and those opposed to clean culture. This law also pro- 
hibited a systematic gathering of all host fruits within a given area, 
thus necessitating many exammations for the removal, as they 
ripened, of the fniits of each single tree. As fiiiits ripen rapidly in 
the semitropics, it proved a physical impossibihty to arrange visits 
of inspectors frequently enough to prevent infested fi-uits from f allmg 
to the ground. 

The data of Tables II and III demonstrate the immense number 
and diversity of host trees and shrubs in Honolulu and the ease with 




Fig. 27.— Ball kamani trees grown for shade and ornament. This tree grows to a large size, and some- 
times in dense thickets in the forest. Its fruits ripen at all seasons of the year and are badly infested by 
the Mediterranean fruit tly. (Authors' illustration.) 

wliich the fruit fly, uncurbed by climatic coiKhtious, finds fruit for 
egg laying during any day of the year. It is absurd to endeavor to 
remove all the fruit from many of the huge trees of the islands. Tliere 
are numerous large trees (figs. 27, 28) beneath which infested fruits 
may be gathered each week in the year, yet the trees are so tall and 
brittle that no inspector can remove the fruits before they ripen. 
One yard in Hilo has 15 host trees from 20 to 50 feet high. To these 
examples might be added many others in which the removal of fruits 
is equally impracticable. Often the fruits of the star apple, for 
instance, ripening in the tops of tall trees do not fall until long after 
they have shriveled up and until after the many larvte developing 
within have matured and dropped from them to the gromid. One 



THE MEDITERRANEAN FRUIT FLY, 



33 



acre of guava or of coffee can support the fly throughout the year 
without the aid of other host fruits and form a center for the 
remfestation of surrounding areas. Notwithstanding the fact that 
the bulk of tlie ripening and infested fruits can be collected except 
during the mango season, lasting from May to July, and fruit-fly 
conditions unquestionably improved from the standpoint of the 
numerical abundance of adult flies, the important fact remains that 
the number of fruit flies that succeed in reaching maturity is suf- 
ficiently large to infest practically every fruit ripening witliin the city. 
Clean culture can not be made effective under present conditions. 
The islands are thoroughly overrun with the fruit fly, and this applies 




Fig. 2S.— The fniits of this tree, the winged kamani, ripening throughout the year, are badly infested by 
the Mediterranean fruit fly. The nuts of this one tree are cnougli to supply adult flies for an entire 
neighborhood. (Authors' illustration.) 

quite as much to the guava scrubs in pastures or lava flows and in 
mountain gulches as within city limits. By far the larger proportion 
of the host trees and shrubs are grown more for protection from the 
tropic sun and for their ornamental value than for their fruits. Large 
numbers of the host fruits are not edible. The destruction of host 
vegetation is out of the question until it can be proved that some 
worth-while advantage can be gained. To cut down all host trees in 
Honolulu at present would mean the removal of a large percentage 
of her prized vegetation without giving her citizens any adequate 
compensation. 



34 BULLETIN 040, TT. S. DEPARTMENT OF AGRICULTURE. 

VALUE OF ELIMINATING HOST VEGETATION. 

In Honolulu many jnango and oraiigo frees were either cut down 
or severely trimmed, but those cut formed too small a percentage of 
the entire host vegetation to serve a practical purpose. The only 
places where the elimination of host vegetation yielded favora])le 
results were about banana and pineapple plantations where the work 
was done in accordance with the regulations of the Federal Horti- 
cultural Board. In these instances the destruction of vegetation did 
not eliminate the adult flies, for these came in from surrounding 
areas. It did, however, lessen the danger of immature stages becoming 
attached to the packing material of bananas and pineapples shipped 
to the mainland. 

Should the Mediterranean fruit fly ever become established in 
California or the Southern States, however, where there is no such 
wealth of native host fruits and where climatic conditions w^ill prove 
an important factor in control, the elimination of host vegetation 
will play a most valuable part in remedial measures. In Algeria the 
infestation of oranges greatly increased after such crops as peaches 
and persimmons were grown. These fruits furnished food for the 
fly during the summer and early fall months, which were for the fly 
starvation months previous to the cultivation of these crops. Aided 
by these summer crops, the fruit fly was able to increase greatly, 
so that when the orange crop began to ripen during the faU and winter 
months the pest could attack it w^ith increased force. In Bermuda 
the elimination of a comparatively few host trees, numerically speak- 
ing, would mean the elimination of breeding places for considerable 
areas. The destruction of unnecessary and valueless host trees will 
not only restrict the breeding ground, but will often so break up the 
sequence of ripening hosts that many adult flies will die while 
attempting to bridge the starvation periods when no fruits can be 
found for egg laying. 

DESTRUCTION OF INFESTED FRUITS AND SPRAYING. 

The destruction of infested fruits and spraying are remedial meas- 
ures that should go hand in hand. In Honolulu they have not given 
satisfactory results for reasons beyond the control of man, as set 
forth on pages 24 to 33. Nevertheless, they can be made successful 
in commercial orchards, if applied with intelligence and persistence 
throughout a neighborhood. One indifferent neighbor can spoil the 
work carried on in surrounding orchards. A community of growers 
must determine in what crop their interests are centered and im- 
partially eliminate nonessential fruits. Then, and, as a rule, not 
until then, will labor spent on tlie destruction of infested fruits and 



THE MEDITERRANEAN FRUIT ELY. 35 

on spraying prove worth while. Sprays are apphed to kill the adults; 
fruits are destroyed to kill the eggs and contained larvae. 



DESTRUCTION OF INFESTED FRUITS. 



Larvae infesting fruits may be killed by submerging the fruits in 
water or by burying, boiling, or burning the fruits. The choice of 
method will depend largely upon the quantity of fruit to be handled 
and upon local conditions. The surest way to kill all immature 
stages of the fruit fly is to boil or burn the fruits. Burning the fruits 
is often expensive and, when trash in compost holes is depended upon 
to furnish the fuel, the burning operation is likely to be unsatisfactory; 
for in Honolulu, at least, the amount of fruit to burn is so greatly in 
excess of the trash that the work is incompletely done. Bringing 
infested fruits to the boiling point will kill all forms of the fruit fly. 
Submerging fruits in ordinary cold water for Ave days will either kill 
all larvae and eggs or prevent their further development. 

Burial in soil is a satisfactory method, provided the fruit is buried 
deep enough and afterwards cracks are prevented from developing in 
the earth above the fruits as the latter decay and settle. It should 
be remembered that just after transforming from the pupa the 
adults are so soft that they have the remarkable ability to force their 
way through incredibly small openings. Hence, a crack in the soil 
extending down to the fruit, even though it be no wider than the 
thickness of ordinary blotting paper, is wide enough to permit the 
adults to reach the surface and so thwart the purpose of fruit burial. 
Adults can not make their way through 1 foot of well-tamped soil, 
but because burial or burning is left to subordinates, who may 
slight the work, boiling or submergence of fruit in water is more 
highly recommended. 

SPRAYING. 

As adult flies can not lay eggs until 4 to 10 days after they emerge 
from the pupa, anything that will kill them during this period is 
useful. Such a remedy has been found in poisoned-bait sprays. 
These are composed of a sweet substance attractive to the flies, 
a poison, and water, Mally, who first used a poisoned spray in control- 
ling this pest, used a formula containing: Sugar, 3 pounds; arsenate of 
lead, 4 ounces; water, 5 gallons. This he applied at the rate of 1 to 
Ih pints to each 10-year-old peach or nectarine tree, Lounsbury 
used 6 pounds of brown sugar, 6 ounces of arsenate of lead paste, 
and 8 gallons of water. Severin used the Mally formula but increased 
the poison to 5 ounces. Weinland used 3^ ounces of arsenate of 
lead, 10 pounds of brown sugar, 5 gallons of plantation molasses, 
and 50 gallons of water. All of these formulas have proved to be 
efficacious. 



36 BULLETIN 640, V. S. DEPARTMENT OF AGRICULTURE. 

Attempts to control the Mediterranean fruit fly under Honolulu 
conditions were unsuccessful. The number of adults killed was 
great, yet a sufficient number survived to infest all fruits that ripened. 
From what is known, however, of the benefits derived from these 
sprays in other countries, there is no question but that poisoned-bait 
sprays, when intelligently applied under such conmiercial conditions 
as exist in California and Florida, will prove successful. Thus MaUy 
in South Africa states that a ' ' severe outbreak of the pest in a commer- 
cial peach orchard was brought to a sudden and practically complete 
halt, and the fruit maturing later was marked under the guarantee of 
freedom from maggots," while the infestation among fruits on check 
trees increased until all fruits became infested. Newman in Western 
Australia estimates the cost of spraying an acre when one applica- 
tion of one pint of spray per tree is made every 12 to 14 days to 
be from $1.50 to $2 per fortnight, and states that this sum is a mere 
bao-atelle to the loss of fruit during a similar period over a like area. 
Both MaUy and Newman, working under conditions of less rainfall 
than obtained at Honolulu, and more like those of California and of 
fall and winter in Florida, beheve that good results will follow the 
consistent application of poisoned bait sprays, particidarly when 
supplemented by the proper destruction of infested fruits. 

Honeybees are not endangered by the application of poisoned- 
bait sprays. 

COLD-STORAGE TEMPERATURES. 

Cold-storage temperatures do not lessen the damage already done 
fruits by larvae within them, but they may become of inestimable 
value in guarding fruits against further attacks while in storage or 
transit and in freeing them from suspicion as carriers of the fruit fly. 

For the details of the effect of cold-storage temperatures upon 
eggs, larvae, and pupae of the Mediterranean fruit fly, application 
should be made to the Bureau of Entomology for articles already 
published. Fruits of almost any variety commonly held in storage 
are held at temperatures varying from 32° to 45° F., with preference 
shown to a range of 32° to 36° F. It may be said that no immature 
stages of the Mediterranean fruit fly can survive refrigeration for 
seven weeks at 40° to 45° F., for tlii*ee weeks at 33° to 40° F., or for 
two weeks at 32° to 33° F. 

It seems reasonable to conclude that sooner or later the certifica- 
tion of properly refrigerated fruit will be practicable. When an 
association of fruit growers, or a people, find it financially worth 
while, there is no reason why they can not operate a central refrigera- 
tion plant under the supervision of an official whose reputation shall 
be sufficient to guarantee all fruits sent out from the plant to be 
absolutely free from danger as carriei's of the fruit fly. 



THE MEDITEREANEAlSr FRUIT FLY. 



37 



PROTECTIVE COVERINGS. 



The only certain method now known of protecting fruit from fruit- 
fly attack in Hawaii is to cover them, when still very green, with some 
type of covering through which the fly can not lay her eggs. In many 
places ordinary cheesecloth sewed into bags, large enough to be slipped 
over the tree and tied about the trunk, have been used. These have 
been tried in Honolulu, but difficulty was experienced in putting the 
bags on soon enough and in making certain that no adult female flies 
were inclosed during the process. 
Considering the cost of material 
and the real danger of inclosing 
flies, the impossibility of covering 
many trees, and the breakage due 
to winds, this method of protection 
is not recommended. 

The protection of the fruit on 
individual branches with cover- 
ings of cloth or paper is entirely 
feasible and very popular in Ha- 
waii, Individual fruits inclosed 
inordinary paper bags (fig. 29) are 
weU and cheaply protected. Cov- 
erings of cheesecloth for separate 
fruits are not as good as paper, for 
the fruit fly can lay her eggs 
through certain coarser-woven 
kinds after the cloth has become 
matted against the fruit by rains. 

Orange and small mango trees 
with their fruits inclosed in paper 
bags are often seen in Honolulu. 
Though this method of covering 
each fruit gives protection, it in- 
volves much labor and patience, 
and its practicability can be de- 
termined oidy by the value placed 
upon the fruit by the owner. So severe, however, is fruit-fly attack 
in Hawaii that this method, or some one of its many modified forms, 
must be used if fruits are to be brought to maturity uninfested. 




Fig. 29.— Quince fruit protected from fruit-fly 
attacli by a paper bag. The bag is slipped over 
the fruit while it is still quite green. Although 
this method of protection is not practical on a 
large scale, it is used much in Hawaii for the 
protection of dooryard or e.xperimental fruits. 
(Original.) 



NATURAL CONTROL OF THE FRUIT FLY. 

No striking examples of control by natural agencies wer(^. evident 
in Hawaii previous to the introduction of parasites. Larvte are killed 
in large nimabers within fruits which are permitted to remain on the 



38 BULLETIN 640, U. S. DEPARTMENT OF AGRICULTURE. 

ground exposed to the direct sunlight in summer, but many larvae 
escape even from such fruits. An examination of 17 mangoes 
exposed over sand on shallow trays to the sun for two days in August 
revealed 17 living and 98 dead well-grown larvse in the fruit, and 103 
that succeeded in safely leaving the fruit to form pupae in the sand 
beneath. The smaU brown ant,* so common about the lowlands of 
Hawaii, unquestionably is a factor in natural control. It is fre- 
quently found swarming over and in fallen fruits and kills many 
larvae as they leave the fruits to pupate. Ants were observed to 
remove from a fallen ball kamani nut 86 medium-sized larvae during 
a 40-minute period, but they failed to reach 34 other larvae in a firmer 
portion of the fruit. 

No natural checks upon fruit-fly increase in Hawaii, aside from 
introduced parasites, are of practical value; but in many other lands 
cHmatic checks are unquestionably of great value, and, as in many 
places in Spain, for instance, are the oidy chocks tliat make fruit 
production possible without the use of remedial measures. 

CLIMATIC CHECKS. 

Observations made in various countries indicate that the Mediter- 
ranean fruit fly will not be a serious pest when the monthly mean 
temperature falls to or below 50° F. for from three to four consecutive 
months during the year. In Hawaii the climate is not cold enough 
throughout the fruit-growing regions to act as a serious check on 
fruit-fly increase. Development progresses most rapidly after the 
Hawaiian means reach 75° to 79° F. At a mean of 68° F. develop- 
ment requires about twice the time. A temperature of 58° to 62° F. 
may increase the period of development to three to four times the 
normal period for the warmest weather. Larval development in 
apples stored outdoors at temperatures ranging from 31° to 64° 
F. (mean, about 51° F.) was slow and was attended by no un- 
usual mortality. No development occurred at 26° to 70° F. 
(mean, 48° F.), and nearly aU larvae were dead at the end 
of six weeks. Very few fruit flies can develop at 49° to 50° F., 
and none at temperatures below this point. Complete mortality 
will foUow continued exposure to temperatures below 50° F. An 
exposure for two to three weeks at 32° F. wiU kill all stages of the 
fruit fly, but an exposure to this low temperature for four days has 
practicaUy no effect upon the fly. Sixty-two of 248 larvae survived 
an exposure for five days to 21° to 28° F. These facts indicate that 
the Mediterranean fruit fly is a very hardy and persistent enemy in 
spite of the quickness with which it responds to checks upon its 
development resulting from the low temperatures ordinarily experi- 
enced in semi tropical countries. 

1 Pheidole megacephala Fab. 



THE MEDITERRANEAN FRTTTT FLY. 



39 



PARASITES. 

The very climatic and host conditions that have made the Medi- 
terranean fruit fly an unusually serious post in Hawaii and that, 
with crop conditions as they are, have made artificial methods of 
control impracticahle, have been most favorable for an attempt 
at control by means of parasites. An abundance of the fruit fly upon 
which to feed and a climate permitting increase each month in the 
year have made conditions ideal. The search for and discovery of 
parasites, and their introduction and establishment where previously 
there had been none, has been one of the entomological romances of 
the present time. The 
parasites now at work 
killing the fruit fly in 
Hawaii have been in- 
troduced by the Ha- 
waiian Board of Agri- 
culture and Forestry as 
a result of the Silvestri 
and the Fullaway- 
Bridwell expeditions 
to Africa. 

These two expedi- 
tions resulted in the 
establishment in the 
islands between May, 

1913, and October, 

1914, of four promis- 
ing parasites : one from 
South Africa,! one 
from eastern Austra- 
lia,^ and two from 
Nigeria,^ West Africa. 
Of these, only one, the 
South African Opius, 
was discovered as a 
parasite of the Mediterranean fruit fly. The tlii'ee others were found 
parasitizing other fruit flies, and they have adapted themselves 
in Hawaii to the Mediterranean fruit fly. None of them, however, 
has been known to attack the melon fly in the gardens in 
Hawaii. Large numbers of all the parasites have been reared and 
have been Uberated in all parts of the islands, until to-day they are 
well able to care for themselves. They have multiplied with 
remarkable rapidity and have unquestionably reduced the numerical 

I Opius humilis Silv. ^ Diachasma tryoni Cam. ' D.fullawayi Silv. an.i Titriialichus giffardianun Silv. 




Fig. 30.— Diagrammatic drawing of a cross section of a coffee cherry 
to illustrate comparative ease with wliich the South African para- 
site can lay eggs in the fruit-fly larva: a, Coffee bean; b, pulp 
destroyed by maggot; c, skin of cherry; d, maggot of fruit fly; e, 
parasite forcing its stinger through skia of cherry into maggot. 
(Original.) 



40 BULLETTTs^ MO, V. S. DEPAETMF.NT OF ACTJTCULTURE, 

abundance of the fruit fly. To-day no batch of infested fruit can be 
collected from which fruit-fly parasites can not be reared. 

Only a beginning has been made in determining the effectiveness 
of parasites as a control factor against the fruit fly in Hawaii. The 
rapidity of estabhshment and the increase of the parasites have been 
very gratifying, yet the data already published recording the per- 
centages of parasitism during the years 1914, 1915, and 1916 indicate 
that while parasitism in thin-meated fruits, such as coffee (see (fig. 30), 
may be consistently very high, in thicker fruits, like the orange, it is 
consistently very low. Thus the parasitism among larvae developing in 
coffee may range between 90 and 100 per cent, while that among larvae 
of the Chinese orange is more likely to range from almost nothing 
to 30 per cent. High parasitism among larvae in such fruits as coffee 
is due to the fact that the larvae are within reach of the parasite. 
On the other hand, the larvae within such fruits as the orange may 
feed about the seeds and therefore remain safe from attack so long 
as they stay at the core, and are subject to attacks only when they 
come to the surface of the fruit. 

Since adult fruit flies can live many months and lay eggs quite 
regularly, they have been able, with the aid of the unprecedented vari- 
ety and abundance of host fruits in Hawaii, thus far to keep such an 
ascendancy over their parasites that they cause the infestation of 
practically all fruits ripening. It would appear that unless effective 
pupal and egg parasites are introduced, or more care is given to the 
elimination of host fruits which more thorougUy protect the larvae 
from parasite attack, or to the planting of fruits which make possible 
the reproduction of large numbers of parasites, httle practical value 
will result from the work of the parasites from the standpoint of ren- 
dering host fruits free from attack. 

Though it seems evident that the favored host fruits will always be 
weU infested if present cultural conditions continue, it is hoped 
that the efficiency of the parasites may be sufficiently enhanced 
to free from attack such fruits as the avocado and the better varieties 
of mangoes. In Kona, Hawaii, where the percentage of parasitism 
in coffee cherries (see fig. 30) has been phenomenally high for tliree 
years, it has not been high enough to free more than an occasional 
cherry from attack. The control exerted by parasites has, however, 
effected a benefit to coffee growers which probably already has repaid 
the Territory of Hawaii for all money expended in the introduction 
of parasites. 

The general effectiveness of control by parasites can be increased 
best by the discovery and introduction of a good egg parasite. 



THE MEDITERRANEAN FRUTT FLY. 
QUARANTINE MEASURES TO PREVENT INTRODUCTION. 



41 



1 



To prevent the Mediterranean fruit fly from becoming established 
in the mainland of the United States, the Federal Horticultural Board 
has promulgated Quarantine No. 13, which provides that its agents, 




Fig. 31.— Chinese laborers inspecting bananas. Each bimch of bananas exported from Hawaii to Cali- 
fornia is inspected for bruised, cracked, or suspicious loolcing fruits. (Original.) 

both in Hawaii and at the mainland ports of entry, shall have strict 
supervision over the movements of all fruits permitted entry to the 
mainland from Hawaii. Quarantine No. 13 makes it unlawful for a 




Fig. 32.— Inspecting bananas as they are unloaded on the dorks ai San Imuih i-ni; inspciaiir iiiikmg cer- 
tain that each bunch bears an inspection tag and has been wrapped in material permitted by law. 
( Photo by Maskew.) 

person to ship or carry any fruit from the Hawaiian Islands except 
ordinary eating bananas, pineapples, taro, and coconuts, and these 
will not be passed by inspectors at ports of entry, such as San Fran- 
cisco, Los Angeles, or Seattle, unless they have been inspected by the 



42 



BULLETIN 640, IT. S. DEPABTMENT OF AGRTCULTUEE. 



Federal agents in Hawaii and bear a Federal certificate of inspection. 
(Fig. 31.) 

In Hawaii every precaution is taken to have bananas and pine- 
apples grown under conditions that will prevent spread of the fruit 
fly. Plantations, packing sheds, and packing materials are inspected 
sufficiently often to insure their being in keeping with the regulations 
of the Federal Board. No fruit can be lawfully accepted for trans- 
portation to the mainland by any transporting company in Hawaii 
until it has been inspected and passed and permits for its acceptance 
have been issued to the transporting company by agents of the Board. 
Furthermore, no fruit can be lawfully removed from ships at ports 
of entry at the mainland unless the permit issued the transporting 
company in Hawaii is found attached to the bill of lading by the 




Fig. 33. — Pineapples never breed fruit flies in Hawaii. To be doubly certain that the pacidng material 
contains no fruit-fly pupae, all crates of pineapples unloaded on the docks at San Francisco are fumigated 
with gas after tarpaulins have been tlirown over the crates to prevent the gas from escaping. (Photo 
by Maskew.) 

Federal agent, and miless each package or crate of fruit bears the 
inspection tag above referred to. (Figs. 32 and 33.) 

Passengers and ships are permitted to take on board in Hawaii 
fruits of all descriptions for consumption while en route to the coast. 
All contraband fruits, however, must be eaten or destroyed before 
the ship comes within the 3-mile limit of the mainland. Otherwise 
the transporting company, or the individual passenger, whichever is 
the offender, is subject to fine or imprisonment, or both. 

SUMMARY. 

The Mediterranean fruit fly has become so thoroughly entrenched 
in Hawaii as a result of favorable climatic and host conditions that 
artificial remedial measures for its control are not practicable. Intro- 
duced parasites have multiplied wonderfully well and already have 
proved of practical value in safeguarding the coffee crop from losses 
due to fruit-fly attack. Though it is certain that the parasites can 



THE MEDITEERANEAN FRUIT FLY. 43 

never exterminate the fruit fly or cause the raising of the quarantine 
against Hawaiian fruits, much ultimate good is expected of them. It 
is hoped that by lessening the abundance of the fruit fly many fruits 
that now become badly infested before they are ripe enough to eat 
may be able to mature uninfested to a point where they will be useful 
to man. At present almost all edible fruits in Hawaii, and many 
ornamentals, making a total of 72 kinds of fruit, are subject to attack. 
Judging from the past history of the Mediterranean fruit fly, only 
the vigilance of quarantine officials and the hearty cooperation of 
travelers will prevent its establishment in California and the Gulf 
States. Every barrier possible has been erected by State and Federal 
quarantines, so that there is now httle danger of the pest gaining 
entry through the medium of commercial shipments of fresh fruits. 
But quarantine officials have found the pest in fruit concealed by 
tourists and in mail and express packages sent from infested countries 
by uninformed persons, and it is by such avenues that the pest is most 
likely to be introduced. These avenues, also, are the most difficult 
of detection, and their closing is dependent mainly upon educa- 
tional campaigns to convince the public of the necessity of quaran- 
tine measures, and upon the unselfishness and personal honesty of 
travelers. At present only bananas, pineapples, taro, coconuts, and 
certain other vegetable products not subject to attack, are permitted 
entry from Hawaii, and these only after the regulations of the 
Federal Horticultural Board have been fulfilled. 



PUBLICATICATIONS OF THE U. S. DEPARTMENT OF AGRICULTURE 
RELATING TO INSECTS INJURIOUS TO CITRUS AND OTHER SUB- 
TROPICAL FRUITS. 

AVAILABLE FOR FREE DISTRIBUTION BY THE DEPARTMENT. 

Control of the Citrus Thrips in California and Arizona. (Farmers' Bulletin (374.) 
Carbon Disiilphid as an Insecticide. (Farmers' Bulletin 799.) 
Common Mealybug and its Control in California. (Farmers' Bulletin 862. 
Fumigation of Ornamental Greenhoiise Plants with Hydrocyanic-acid Gas. (Farm- 
ers' Bidletin 880.) 
Fumigation of 'Citrus Trees. (Farmers' Bulletin 923.) 
Control of the Argentine Ant in Orange Groves. (Farmers' Bulletin 928.) 
Spraying for the Control of Insects and Mites Attacking Citrus Trees in Florida. 

(Farmers' Bulletin 933.) 
Citrus Fruit Insects in Mediterranean Countries. (Department Bulletin 134.) 
The Mediterranean Fruit Fly in Bermuda. (Department Bulletin 161.) 
Katydids Injurious to Oranges in California. (Department Bulletin 256.) 
Argentine Ant: Distribution and Control in the United States. (Department 

Bulletin 377.) 
The Melon Fly in Hawaii. (Department Bulletin 491.) 

Fumigation of Ornamental Greenhouse Plants with Hydrocyanic-acid Gas. (Depart- 
ment Bulletin 513.) 
The Mediterranean Fruit Fly in Hawaii. (Department Bulletin 536.) 
The Citrus Thrips. (Department Bulletin 616.) 
The Mellon Fly. (Department Bulletin 643.) 
Some Reasons for Spraying to Control Insect and Mite Enemies of Citrus Trees in 

Florida. (Department Bulletin 645.) 
The Argentine Ant in Relation to Citrus Orchards. (Department Bulletin 647.) 
Preparations for Winter Fumigation for Citrus \\Taite Fly. (Entomology Circular 111.) 
Spraying for AMiite Flies in Florida. (Entomology Circular 168.) 

FOR SALE BY THE SUPERINTENDENT OF DOCUMENTS, GOVERNMENT PRINTING 
OFFICE, WASHINGTON, D. C. 

Mango Weevil. (Entomology Circular 141.) 1911. Price, 5 cents. 

Fumigation for Citrus WTiite Fly, as Adapted to Florida Conditions. (Entomology 

Bulletin 76.) 1908. Price, 15 cents. 
Fumigation Investigations in California. (Entomology Bulletin 79.) 1909. Price, 

15 cents. 
Hydrocyanic-acid (lias Fumigation in California. (Entomology Bulletin 90, 3 pts.) 

1913. Price, 20 cents. 
Fumigation of Citrus Trees. (Entomology Bulletin 90, pt. I.) 1913. Price, 20 cents. 
Value of Sodium Cyanid for P'umigation Purposes. (Entomology Bulletin 90, pt. 

II.) 1913. Price, 5 cents. 
Chemistry of Fumigation with Hydrocyanic-acid Gas. (Entomology Bulletin 90, 

pt. III.) 1913. Price, 5 cents. 
\Vhite Flies Injurious to Citrus in Florida. (Entomology Bulletin 92.) 1911. Price, 

25 cents. 
Orange Thrips, Report of Progress. (Entomology Bulletin 99, pt. I.) 1911. Price, 

5 cents. 
Red-banded Thrips. (Entomology Bulletin 99, pt. II.) 1912. Price, 5 cents. 
Natural Control of White Flies in Florida. (Entomology Bulletin 102.) 1912. Price, 

20 cents. 
44 

o 



a 



lliiii 



11 



Caylord Bro& 

Makers 

Syracuse, N. Y. 

PAT. JAN. 2U lU^ 



!i!i 



' 



